On the other hand, when adapting a larger-format lens to your camera, you’ll have a generous image circle, but a narrower angle of view. Larger formats have larger image areas, and require lenses with longer focal lengths. So, while a wide-angle lens on a full frame DSLR might be 21mm, the equivalent field of view on a medium-format camera requires a 50mm lens, and on a 4x5 format, 90mm. But when you put the 50mm wide-angle medium-format lens on your DSLR, it stays a 50mm lens and offers a normal perspective. In effect, the widest medium-format lenses become normal lenses on a full-frame DSLR, whereas the widest lenses for large-format camera systems become short teles. On APS-C and Four Thirds cameras, these lenses have still longer focal length equivalents.
While the quality of many medium- and large-format lenses can be high, they tend to be heavier and more expensive than DSLR lenses. Furthermore, large-format lenses cannot be adapted to a DSLR unless attached to a special bellows adapter—although in doing so you gain access to a number of useful perspective and plane-of-focus camera movements such as tilt and shift. (You can also take advantage of the larger image circle of medium-format lenses and use them with bellows adapters on a DSLR for the same purpose.)
But for anything other than very precise critical work, you’re probably better off buying a dedicated tilt-shift lens to gain these large-format camera movements on your DSLR, without the technical hassles of adapting.
If you don’t like losing autofocus and auto aperture, consider having your alternative lens permanently modified by a professional service. Conurus in Vancouver, BC, Canada (conurus.com) is a leader in modifying alternative lenses for certain cameras. Modified lenses retain autofocus, auto aperture, and EXIF communication. Current options include Contax N lenses to Canon EOS cameras, Canon EF lenses to Sony NEX cameras, and Contax N lenses to Sigma SD14 cameras. Expect to pay anywhere between $300 and $1,000 for modification, depending on the lens.
Glitches and Gremlins
When using a lens adapter don’t expect everything to work as usual. Besides losing autofocus and auto aperture, your lens won’t communicate EXIF data to the camera. And if that weren’t enough, you might even experience firmware conflicts. For example, I’ve used my Nikon 14–24mm lens on my Canon EOS 5D Mark II with no problems, but when I upgraded to the 5D Mark III, working in live view was rendered impossible. The problem? The new firmware for the Mark III didn’t like the data coming from the adapter’s focus-confirmation chip. So I pried off the chip. Problem solved!